JPS5826617B2 - The first thing you need to know - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a neutron detector that is easy to manufacture and has excellent accuracy.

The power of a nuclear reactor is usually measured by measuring neutrons.

In addition to the neutrons that cause nuclear fission, the radiation that enters the neutron detector from the nuclear reactor includes gamma rays that are generated as a secondary source.

These gamma rays ionize the gas in a normal neutron detector, and in addition to the ionizing current due to the neutron reaction, an ionizing current due to gamma rays flows through the detection circuit, but this current due to gamma rays is proportional to the neutron flux. First, it becomes an obstacle to the measurement of the current caused only by neutrons, that is, the neutron flux.

Therefore, a gamma-ray compensated neutron detector (
(hereinafter referred to as C, I, and C0).

As shown in Figure 1 a+b, these C0■, C are (a) 3
It is composed of two electrodes, namely an anode, a signal electrode 2, and a cathode 3.

(b) Moreover, these three electrodes 1 to 3 have different inner and outer diameters and are arranged concentrically.

(c) The opposing surfaces of the signal electrode 2 and the anode 1 are coated with a substance that reacts with neutrons, such as boron IT l OB-15.

The discharge region 4 formed by the opposing surfaces due to both neutron reaction products and gamma rays is filled with N2 gas.

The γ-rays directly ionize the N2 gas molecules due to the photoelectric effect or the like.

The δ rays generated by ionization continuously ionize the N2 gas encountered during the flight, and an ionization current ■γ due to the γ rays flows.

The neutron is captured by boron et 10 B II 5 and ionizes N2 gas molecules by the 7Li nucleus and α rays due to the 7Li reaction, each ionized 1
．． and In flows.

) The γ formed by the opposing surfaces of the signal electrode 2 and the cathode 3 (no neutrons and reactants are coated here)
The discharge area 5 formed only by the wire is also filled with N2 gas.

Since this tl-boron 10B''6 is not coated, neutrons pass through without causing any reaction, and an ionization current of N2 gas only due to γ rays flows from the signal electrode 2 to the cathode 3.

(e) At this time, if the electrical effective volumes of the two discharge regions are made equal, ionization currents due to the γ rays that are pressed in the two discharge regions can be obtained with equal absolute values.

(f) In order to equalize the effective electrical volumes of the two discharge regions, the cathode 3 is constructed as shown in FIG. 2, and conventionally this was cut out from a round metal bar by lathe processing or the like.

This cathode 3 has several hundred grooves 31 (groove width L0-
Mountain width L221~2t [1m1 tolerance several tens of μm, groove depth d=
5 to 10 mm).

(g) As shown in Fig. 1, the cathode 3 constructed in this way is connected to the anode 1 with ten voltages and the cathode 3 with one voltage applied using the DC power supply 7, and the signal electrode 2 is grounded through the DC current measuring device 8. It is exposed to electric potential.

It was wired like this.

When C, I, and C are irradiated with neutrons and γ-rays, ionization current In due to neutron reaction products and ionization current Ir due to γ-rays flow from anode 1 to signal electrode in discharge region 4 due to both neutrons and γ-rays. Flows towards 2.

On the other hand, in the discharge region 5 caused only by gamma rays, an ionization current I'r caused by gamma rays flows from the signal electrode 2 toward the cathode 3.

That is, the current flowing from the signal electrode 2 through the DC current measuring device 8 and reaching the ground becomes In+Ir+Ir.

Here, since ■r and I'r have equal absolute values and opposite polarities, only the ionizing current In that compensates for the ionizing current due to γ rays flows through the DC current measuring device 8.

The conventional manufacturing method for the cathode 3 (Fig. 2) for C, I, and C is to create an integrated electrode using a single round metal bar through high-precision lathe processing. Because it was made by hand, it took time and money to manufacture it, and it was difficult to achieve dimensional accuracy.

Moreover, they have the disadvantage of being susceptible to deformation and damage during handling such as storage and transportation.

This invention has been made to eliminate the above-mentioned drawbacks.

This invention will be explained below. FIG. 3 shows an embodiment of the present invention, showing only the structure of the cathode 3'.

Reference numerals 11 and 12 denote two kinds of donut-shaped disks punched out from the plate, namely, a large outer diameter disk and a small outer diameter disk, and their perspective views are shown in FIG. 4, respectively.

Alternately combine these with bolts 13, nuts 14, etc.
It is constructed into a cylindrical electrode 3' having the same shape as the cathode 3 shown in the figure.

The other configurations are the same as in FIG.

With this configuration, it is possible to provide a cathode that solves problems such as time, cost, precision, deformation, and damage all at once.

Although the above description has been made regarding C0■ and C0, the present invention can also be applied to, for example, a boron 1°B II ionization chamber.

The conventional boron "10B" ionization chamber is a two-electrode DC ionization chamber, as shown in Figure 5, in which boron "IOB" 6 is applied to the opposing surfaces of the anode 21 and cathode 22, which are made up of two parallel cylinders. This is what I did.

As shown in the figure, an anode 21 and a cathode 22 having a cross section in which large diameter parts and small diameter parts are alternately arranged are used in order to increase the area of the film made of boron 610B"6 as much as possible in order to improve the current sensitivity to neutrons.

The production of such an anode 21 and cathode 22 is as shown in FIG.
There were processing problems just like in the case of .

An embodiment in which the present invention is applied to such a boron "10 B" ionization chamber is shown in FIGS. 6a and 6b.

As the cathode 22', one constructed similarly to the cathode 3' shown in FIG. 3 is used.

As the anode 21', a large inner diameter circular plate 23 and a small inner diameter circular plate 24 shown in FIG.
The anode 21' can be easily constructed by forming an appropriate number of discs 5, arranging these discs alternately, inserting bolts 26 into the through holes 25, and fixing them with nuts 27.

As described in detail above, the present invention provides a neutron detector equipped with at least one electrode in which large diameter portions and small diameter portions are alternately formed, and the electrodes are connected to holes with different inner or outer dimensions. Since it is constructed by stacking open metal plates alternately, compared to those formed by cutting from a single piece of material,
It has the advantage of not only significantly reducing production time and costs, but also solving problems such as accuracy, deformation, and damage all at once.

[Brief explanation of the drawing]

FIGS. 1a and 1b are a side sectional view and a front sectional view showing simplified structure buttons and connections of conventional C01 and C, and FIG. 2a is a front sectional view. b is a side cross-sectional view and a front view showing a conventional cathode, FIG. 3 is a side cross-sectional view of a cathode showing an embodiment of the present invention, and FIG. Perspective view of a small outer diameter disk,
FIG. 5 is a half-sectional view of a conventional boron "10B II" ionization chamber, FIG. The figure is a perspective view showing a large inner diameter disk and a small inner diameter disk in the embodiment of FIG. 6, respectively. In the figure, 3' is a cathode, 11.12 is a donut-shaped disk, and 21
' is an anode, 22' is a cathode, 23 is a large inner diameter disk, and 24 is a small inner diameter disk. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] In a neutron detector equipped with at least one electrode in which 1 meter diameter portions and small diameter portions are alternately formed, the electrode is constructed by alternately stacking metal plates with holes having different inner or outer dimensions. A neutron detector featuring